The present invention relates to a process for the production of precipitated calcium carbonate particles structured at the nanoscale.
Particles of calcium carbonate precipitated by carbonation of milk of lime, by virtue of their high purity, are highly suitable as filler, in particular in paper and plastics. These applications also require very fine particles.
It is known (WO 99/51691) to produce precipitated calcitic calcium carbonate by carbonation of milk of lime in the presence of soluble organic compounds, such as citric acid, at very low concentration, of the order of 0.1%. However, the calcite particles obtained are too large to be actually used as filler in plastics.
U.S. Pat. No. 4,157,379 discloses fibrous particles, structured at the nanoscale, of precipitated calcium carbonate which are composed of the agglomeration, as a chain, of primary corpuscles having a mean diameter of between 10 and 100 nm.
However, these particles require a complex two-stage carbonation of the milk of lime; in the first stage, a chelating agent is added to the milk of lime to form a colloidal suspension; the latter is subsequently carbonated in the presence of another additive, a soluble metal salt, everything being under controlled pH.